The invention relates to a two-substance spray nozzle with a mixing chamber disposed in a housing in front of a discharge opening, into which opening feed passages bearing a liquid and a gaseous medium enter and in which a target body is provided, against which target body the liquid stream strikes.
In such two-substance spray nozzles with internal mixing, the gas is introduced in finely divided form into a liquid stream and the more or less homogenous mixture is carried out through the narrowed discharge orifice.
DE 31 31 070 C2 discloses a two-substance spray nozzle that is situated opposite an entry opening for the liquid, where a target table was arranged in a mixing chamber. The face of the target table is disposed in the center of a mixing chamber, perpendicular to the axis of the liquid stream and in line with the delivery axis of the gaseous medium. The liquid stream impinging upon the target table therefore bursts in the mixing chamber and is entrained by the compressed air delivered perpendicularly thereto. The liquid stream is divided as uniformly as possible as it continues through the mixing chamber and then is delivered through a discharge opening lying on the axis of the opening through which compressed air is delivered.
In another type of construction according to DE-OS 22 52 218, the liquid stream impinges at the end of a mixing chamber upon a target plate and is mixed with air which is introduced tangentially into the mixing chamber situated in front of the target plate. The mixture thus produced by the turbulence then enters an annular channel behind the target plate and is delivered to an opening which is followed by a second target plate.
An object of the present invention is a two-substance spray nozzle that can achieve a highly uniform mixture between liquid and gaseous phases, which is not easily achievable and could be achieved only by mixing chamber arrangements which require a comparatively great amount of space.
To achieve this object, a two-substance spray nozzle includes an anvil that is designed as a deflecting body aligned coaxially with the liquid stream. The deflecting body flares out in the direction of flow until it reaches a spill-over rim and has an apex pointed against the flow of the liquid. The passages for feeding the gaseous medium lead into the part of the mixing chamber that surrounds the flaring portion of the deflecting body. With this configuration the liquid entering in the form of a solid jet is divided starting from a spreader apex into a liquid film whose thickness diminishes with increasing diameter of the deflection body. Against this relatively thin liquid film the gaseous medium is directed at the spill-over rim of the deflecting body and breaks it up into fine droplets inside of the nozzle. Since in this kind of configuration the liquid film can be uniformly distributed over the circumference of the deflection body, a largely homogeneous mixture with the air is achieved, which leads to a range of droplet sizes of great uniformity.
In a further development of the invention, the passages feeding the gaseous medium can discharge in the direction of flow upstream of the spill-over rim, and can run approximately parallel to the direction of the flow of the liquid stream. This brings the advantage that the passages carrying both media can be brought to a common junction point, and not perpendicular to one another and not requiring a relatively great amount of space as is the case with two-substance nozzles according to the state of the art.
In an embodiment of the invention, the inside wall of the mixing chamber can run approximately parallel to the contour of the deflecting body, so that the air to be mixed with the liquid can be brought close to the deflection body and to the spill-over rim where mixing with the liquid film ring takes place.
The deflection body can be configured as a pyramid. Simply, however, it can he configured as a cone whose axis coincides with the axis of the delivery of the liquid. In an advantageous embodiment it is also possible to configure the deflection body as a double cone which flares in the direction of flow down to the spill-over rim and then tapers back again. This embodiment, together with the correspondingly narrowing inside wall of the mixing chamber, makes it possible to locate the discharge opening or openings downstream of the spill-over rim. Thus also the mixing area is thereby prescribed, which due to the configuration of the invention, does not, of course, require an excessively great length of flow.
In another embodiment of the invention, the flare angle of the cone can be enlarged in the area of the spill-over rim, so that a circumferential margin will form the greatest diameter. With this measure, the liquid film is deflected into a plane approximately perpendicular to the entering air, which enhances the mixing action.
In a further embodiment of the invention, the discharge port can include a plurality of discharge bores whose number, position and exit angle can be chosen according to the desired spray angle and spray stream. One of the important factors to the invention is the distribution of the delivered liquid into an increasingly thin liquid film and its mixture with the air delivered to the area of the spill-over rim of the deflecting body.